We’ve seen ourselves in the heavens. A giant spiral galaxy 180 million light years from Earth not only resembles the Milky Way but also boasts a pair of interacting galaxies that look like our galaxy’s two brightest satellites.

At least 50 galaxies orbit the Milky Way. Most have run out of gas because they’ve spent more time close enough to our galaxy for it to steal their gas. But two of the nearest satellites – the Large and Small Magellanic Clouds – have been in our neighbourhood for less time, and still possess lots of gas that spawns new stars. The two galaxies are respectively 160,000 and 200,000 light years from us and 75,000 light years from each other.

This arrangement is rare. Most giant galaxies don’t have even one star-making companion nearby, let alone two. That’s probably because a giant galaxy strips small neighbours of gas, thwarting their ability to make new stars.

Sanjaya Paudel and Chandreyee Sengupta at Yonsei University in Seoul, South Korea, looked through images of nearly 20,000 small galaxies for a pair that resides near a giant galaxy. “It’s obviously very difficult,” says Paudel.

Bridge of stars

Nevertheless, the astronomers succeeded, finding a giant barred spiral galaxy in the constellation Hydra named NGC 2718 that resembles the Milky Way. Moreover, it has two bright star-forming companions named UGC 4703. A bridge of young stars connects the two smaller galaxies, indicating they are interacting with each other, just as the Magellanic Clouds are.

“They have definitely found a better analogue than any of the cases we presented,” says at Liverpool John Moores University, who in 2011 published the results of a search for such systems and found them exceedingly rare.

“This one is particularly interesting because it is clear that the two smaller galaxies are interacting,” says at the University of Arizona in Tucson. “That wasn’t as clear in any of the other existing analogues.”

How can star-making galaxies thrive next to a gas-grabbing giant galaxy? The Magellanic Clouds probably fell toward us only recently, so the Milky Way hasn’t had time to steal much of their gas. Paudel says the same explanation may hold for the newfound galactic trio in Hydra.

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Read more: Intergalactic collision birthed a sparkling ring of young stars

A ring has been found around Haumea, a world more than 2 billion kilometres beyond Pluto. The ring is the most distant ever seen in our solar system.

“This is a landmark discovery,” says at the Southwest Research Institute in Boulder, Colorado. “It’s very exciting.”

Until recently, the only known rings circled giant planets such as Saturn. In 2013, however, astronomers found two rings around Chariklo, an odd little rock about 250 kilometres across between the orbits of Saturn and Uranus. Chiron, one of Chariklo’s neighbours, may also have a ring.

Now astronomers have found a ring beyond Neptune. and at the Institute of Astrophysics of Andalusia in Granada, Spain, and their colleagues watched the dwarf planet Haumea pass in front of a dim red star in the constellation Boötes on 21 January this year. A total of 12 telescopes in six European countries tracked the eclipse.

The duration of the eclipse revealed Haumea’s size and shape. But before and after it moved completely in front of the star, a ring around Haumea’s equator blocked some of the starlight. “It was really an amazing surprise,” says Santos-Sanz. The ring is 70 kilometres wide and about 2290 kilometres from Haumea’s centre.

Spinning like a top

“This is fabulous. It’s a really great discovery,” says at Washington University in St Louis, Missouri.

He says that Haumea’s many odd properties may provide clues on how it came to have a ring in the first place. The far-off world is shaped like an egg, which may result from its whirlwind rotation. Haumea completes a full spin every 3 hours and 55 minutes, whereas the dwarf planet Pluto, which is almost perfectly round, rotates every 6.4 Earth days. Every 24 hours, a resident on Haumea’s equator would see six sunrises and six sunsets. It also has two small moons.

McKinnon suspects that all these traits are linked. He thinks a large object may have hit Haumea, causing it to spin and eject debris that created both the ring and the moons.

This impact would also explain another phenomenon: several other bodies travel on almost the same path around the sun as Haumea and share its composition, having water ice on their surfaces. They could all have been born during the same initial smash-up.

Shiny new worlds

Ortiz and Santos-Sanz also found that Haumea is slightly larger than once thought: at its widest, it is nearly the diameter of Pluto, the largest-known object orbiting the sun beyond Neptune. It is, however, only about 1025 kilometres across at its narrowest point, less than half Pluto’s diameter.

It is also much less dense than previously thought and has a make-up similar to Pluto’s. Both worlds are mostly rock, surrounded by water ice. And both are shiny, reflecting about half the light that strikes them.

Stern says all these interesting properties could make Haumea a good candidate for an exploratory visit from a spacecraft such as NASA’s New Horizons probe, which sped past Pluto in 2015.

In fact, New Horizons has just begun its own search for rings around dozens of distant worlds. “What we want to know is,Ěýare these rings rare or routine?” says Stern, who is principal investigator for New Horizons.

The spacecraft is heading in the wrong direction to study Haumea, but Stern says we could launch a probe its way. “Given the object’s egg shape, two satellites and ring, it would be a really amazing place to go visit,” he says.

Journal reference: Nature, DOI:

Read more: Saturn’s rings may be from the whirl of a passing icy rock

A small galaxy in the constellation Lynx that only recently started making stars has the lowest level of oxygen ever seen in a star-forming galaxy. That makes it the best place yet to probe the chemical elements cooked up by the big bang.

The big bang produced just three main elements: hydrogen, helium and a little lithium.ĚýThus, the first galaxies presumably had little oxygen, but are so small and remote that we can’t see them.

So Yuri Izotov at the Main Astronomical Observatory in Kiev, Ukraine, and his colleagues hunted for star-forming galaxies closer to home that resemble the primordial ones by having little oxygen.

“They are very rare,” says Trinh Thuan at the University of Virginia in Charlottesville. That’s because star-forming galaxies have massive stars that explode soon after birth, raising the oxygen level.

Hunting for helium

The astronomers used the Sloan Digital Sky Survey in New Mexico to look for galaxies with little oxygen.ĚýUp came a smudge 620 million light years away that they named J0811+4730.

Data from the Large Binocular Telescope in Arizona revealed this galaxy to be a record-breaker, bearing 9 per cent less oxygen than the previous champ.ĚýIts oxygen-to-hydrogen ratio is only 1.7 per cent that of the sun, which has 1 oxygen nucleus for every 1740 hydrogen nuclei.

Some dwarf galaxies have even less oxygen, but the new galaxy is special because it’s doing something that they are not:Ěýcreating new stars from its gas. The hottest of these stars strip electrons from helium gas, so observers can measure that element’s abundance.

“If we want to know the primordial helium abundance, we’ve got to look at these galaxies,” says Grant Mathews at the University of Notre Dame in Indiana. Finding this out helps reveal the conditions that prevailed during the first three minutes of the universe’s life, because helium was one of the few elements created by the nuclear reactions right after the big bang.

Small but mighty

The new galaxy is important for another reason:Ěýit gives us a close-up look at the type of vigorous dwarf galaxies that probably reionised the early universe. Reionisation marked the transition from the time when neutral gas pervaded the universe to the state it has today, when the gas between galaxies is ionised.

The new galaxy is both a pipsqueak and a powerhouse. Its stellar mass is only one-thirty-thousandth that of the Milky Way.ĚýYet it’s churning out new stars at a quarter the rate of the Milky Way – an impressive feat for such a tiny galaxy.

In fact, says Thuan, the newly found galaxy spawned 80 per cent of its stars in just the past few million years. The hottest of these stars emit the same kind of blistering radiation that reionised the universe shortly after the big bang. The galaxy serves as a surrogate for the galaxies we can’t yet see that transformed the entire cosmos some 13 billion years ago.

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Read more: Spiralling galaxy arms spread oxygen around for future planets

Distorted ring

Desdemona’s doom

You may be able to thank the Milky Way’s spiral arms for supplying Earth with a fair share of the vital element at our planet’s birth.

Oxygen is the third most abundant chemical element in the universe, after hydrogen and helium. It arises mainly in massive stars, which forge the element during their brief lives and then cast it into space when they explode.

But a galaxy’s spiral arms also help spread the wealth, saysĚýĚýat the Max Planck Institute for Astronomy in Heidelberg, Germany.

He and his colleagues have measured oxygen levels throughout a galaxy named NGC 1365 located 60 million light years away in the constellation Fornax. It has two gargantuan spiral arms joined together by a bar of older stars, all embedded in a huge disc of stars and interstellar gas and dust. As viewed from Earth, the galaxy rotates clockwise, but most of the stars and gas revolve faster than the spiral arms themselves.

Ho’s team has discovered that oxygen is 60 per cent more abundant in the spiral arms than in gas that has just passed through them.

Ěý“To the best of our knowledge, this is the most extreme case so far,” Ho says.ĚýIn contrast, using older instruments, astronomers have failed to detect any variations in oxygen levels as one proceeds clockwise around most spiral galaxies.

We can’t see our galaxy from the outside, so it’s harder to do this in the Milky Way. Nevertheless, there are hints of such variation in our galaxy too.

In a spin

“It’s certainly a fascinating observation,” says at IBM Research in Yorktown Heights, New York.Ěý “It would not have been predicted, I think, and that’s why it’s so interesting.”Ěý Understanding the result, he says, will require simulations that incorporate spiral arms, star formation, supernova explosions and oxygen enrichment.

Ho thinks that as gas that has just passed through a spiral arm revolves toward the next arm, massive stars within the gas explode, raising the oxygen level. The next generation of newborn stars inherit this oxygen and raise the level further when they explode.ĚýThe abundance rises until the gas levels reach a peak in the next spiral arm before turbulence again begins to dilute it.

Then turbulence in the spiral arm mixes the oxygen-rich gas with other gas, diluting it.ĚýThat explains why gas that has just passed through a spiral arm is lowest in oxygen.

By spreading the oxygen around, however, the spiral arms help distribute the element far and wide so that oxygen eventually makes its way into future generations of stars and planets elsewhere in the galaxy.

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Read more: Galaxy’s rapid growth spurt may have spawned 3000 suns per year

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Black hole’s pull

Prodding relativity

Talk about rocking the cradle.ĚýSharp new images have identified a throng of newborn stars as the source of a fast radio burst.ĚýThe discovery strengthens the idea that these brief pulses of radio waves arise from newly formed neutron stars, super-dense objects just 20 kilometres across.

During the past decade, astronomers have detected about two dozen fast radio bursts from all over the sky. Each lasts just a few milliseconds, and attempts to explain them have invoked everything from supermassive black holes to little green men.

Until recently, we didn’t even know for sure whether the bursts arose in our galaxy or beyond. But in January, researchers announced a breakthrough.ĚýThey found the home of a fast radio burst named FRB 121102: a small galaxy in the constellation Auriga 2.4 billion light years from Earth.

Now, Cees Bassa of the Netherlands Institute for Radio Astronomy in Dwingeloo and his colleagues have used the Hubble Space Telescope to study the galaxy.

“The Hubble observations allow us to get a very sharp image,” says team member of McGill University in Montreal, Canada. “There is a very bright spot of star formation, and this FRB lies bang inside it.”

Meanwhile, Japanese astronomers led by of Tohoku University in Sendai used the 8.2-metre Subaru Telescope in Hawaii to target the galaxy.ĚýTheir images rival Hubble’s because adaptive optics undid the usual blurring created by Earth’s atmosphere.

The Hubble and Subaru images show that the star-forming complex lies on the small galaxy’s outskirts. Hubble’s handiwork puts the galaxy’s visible diameter at about 20,000 light years, one-sixth that of the Milky Way.ĚýThe stellar nursery is 6200 light years from the galaxy’s centre and spans 4400 light years, far larger than any known in the Milky Way.

Prolific galaxy

“It’s an extraordinary galaxy,” says of the National Radio Astronomy Observatory in Socorro, New Mexico.Ěý“Relative to its small size, it’s making stars at a prolific rate.”

That points to the cause of fast radio bursts.Ěý“It’s telling us that they probably occur in young neutron stars,” says of Washington University in St Louis, Missouri.

Many astronomers already favour that explanation because the short duration of the bursts suggested the source was tiny.ĚýNeutron stars fit the bill, and young, fast-spinning ones have plenty of energy to release.ĚýThey form when short-lived massive stars die in their stellar nurseries.

But no one yet knows whether the same idea explains other fast radio bursts.ĚýFRB 121102 is unique:Ěýastronomers have seen it flash about 30 times but the others only once.

Katz suspects they may all have the same cause, but Frail says, “I would be reluctant to draw such broad conclusions based on a sample of one.”

Journal reference:Ěý and

Watching them revolve

It’s not easy to make Earth.ĚýMost of the explanations for how our planet formed have troubling problems. But if a new idea is right, we can thank a hyperactive young sun for Earth’s existence, plus solve a long-standing mystery about Mars.

According to standard lore, the planet-building process began when dust particles orbiting the newborn sun stuck together, forming rocks that built still larger objects.

But this story is in trouble. “I’ve been really, really disturbed by the problem of making terrestrial planets,” says at the American Museum of Natural History in New York.

These planets are the first four from the sun: Mercury, Venus, Earth and Mars.ĚýThey’re mostly made of rock and iron – whose particles don’t readily stick together.

They could have been sticky enough if they had a coating of snow and organic goo, Hubbard says. But despite all Earth’s oceans and carbon-based life, our planet has too little water or carbon to support this explanation.

Now Hubbard has suggested an intriguing solution to Earth’s difficult birth.ĚýIn 1936, an infant star began to brighten, eventually shining over 100 times more brightly than it did originally.ĚýNow named FU Orionis, this star has stayed bright ever since.ĚýAnd several other stellar youngsters have done the same thing.

Here comes the sun

What if the newborn sun also did this?ĚýThe outburst would have partially melted dust grains, making them sticky enough to become the seeds of Mercury, Venus, Earth and Mars.

“You naturally expect a terrestrial planet pattern that looks a lot like our own solar system if you have an FU Orionis-type event,” Hubbard says.

Meanwhile, in solar systems that didn’t experience such an eruption, dust grains would only be molten closer to the star, leading to compact systems like Kepler-11, as other astronomers .

“It’s an interesting idea,” says at the University of Arizona, noting the difficulty of explaining terrestrial planet formation.Ěý“There’s clearly a major problem here, and so all ideas need to be looked at.”

Hubbard’s model also explains diminutive Mars, which is only half the diameter of Earth.

“Mars is pretty darn small,” he says.ĚýMost scientists blame gravitational interference from giant Jupiter, an idea dating back to Prussian philosopher Immanuel Kant in 1755.

But Jupiter may be innocent.ĚýAn FU Orionis outburst wouldn’t melt dust grains much beyond Earth’s orbit.ĚýAt the Red Planet’s distance, Hubbard says, “the peak temperature didn’t get high enough long enough for the molten grains to grow big enough”.

As a result, Mars had little material to form from and so ended up only 11 per cent as massive as Earth, he says.